Survivors of the December 26th tsunami fled their homes in terror last night after a huge undersea earthquake measuring up to 8.7 on the Richter scale struck off the coast of Sumatra, leaving many dead close to its epicentre.
Ninety-three days after giant waves left nearly 300,000 people dead or missing, there were reports of up to 300 fatalities on the Indonesian island of Nias.
"A powerful earthquake off the Indonesian island of Sumatra is spreading panic but there have been no reports yet of it triggering any tsunamis," UN Emergency Relief Co-ordinator Jan Egeland said in New York.
However, the earthquake caused a small tsunami on the Cocos Islands in the Indian Ocean and waves could spread toward Mauritius and Madagascar, US experts warned. The Cocos lie to the south of the epicenter of the quake.
Nias's main town was likely to be 75 per cent damaged, local police said. Residents were said to be trapped in damaged buildings after the earthquake struck on the same faultline as the St Stephen's Day quake, 250 miles south-east of Banda Aceh.
The deputy police chief in Gunungsitoli town, Nias, said: "Many people are hurt and many are still trapped in buildings. The earthquake was massive, it's still shaking now."
Agus Mendrofa, a district official on Nias island said: "Hundreds of buildings have been damaged or have collapsed. We're not sure about casualties, but there may be dozens of people buried in the rubble."
At least 340 Nias residents died and 10,000 were left homeless in the December 26th earthquake.
With a tsunami warning system for the Indian Ocean still the subject of political debate, governments in Thailand, India and Japan attempted to warn local people over radio and TV after the earthquake struck 19 miles under the Andaman Sea at 11.09pm local time.
In the Indonesian province of Aceh, tens of thousands of people abandoned tents and temporary homes and ran for high ground in darkness when the earth shook for two minutes, far longer than the much smaller quakes that have rocked the area in recent weeks.
Electricity and phone lines were down across much of Sumatra as the earthquake was felt as far away as Bangkok and Singapore, where tall buildings swayed.
Recorded at 8.7 by the US Geological Survey and 8.5 by Japan's Meteorological Agency, with an epicentre farther south than the Stephen's Day earthquake, seismologists warned that the latest earthquake had the potential to create another destructive tsunami at the end of a week of at least seven smaller aftershocks in the region.
In Thailand, cracks in buildings appeared, apparently caused by the quake, in southern provinces and people were evacuated from hotels and hospitals in Phuket, Phang-nga and Krabi, the areas worst affected by December's tsunami.
"About 3,000 to 4,000 tourists and locals have been evacuated from Patong and Kamala beaches to higher places," Wichai Buapradit, the deputy governor of Phuket, told Reuters.
Sirens rang out in Sri Lanka as towns on the east coast began frantically evacuating residents.
Scientists last week predicted a magnitude 7.5 earthquake was possible in the region after the seismic slip on December 26th had piled dangerous levels of stress on to two vulnerable parts of the fault zone off the coast of Sumatra.
The December 26th event measured 9 on the Richter scale and left 1.5 million homeless across 11 countries.